drivers/sensor: lsm6dso: improve sensorhub code

1. Fix sensorhub names using the zephyr A.2 rule (use inclusive language).
   The only exception is names within STMEMSC API and h/w register names.

2. Extend the STMEMSC API usage. It is always better to not code again
   already existing functionalities.

Signed-off-by: Armando Visconti <armando.visconti@st.com>